Multicellular plastic particles and dispersions thereof



B. L. RASKIN Feb. 27, 1968 MULTICELLULAR PLASTIC PARTICLES ANDDISPERSIONS THEREOF 2 Sheets-Sheet 1 Filed Aug. 9, 1965 mozmddww M2055wZEEDk mowmwmaou v o R 0 mm E v% N A R U m VI T T E B 4] E3 Feb. 27,1968 B. L. RASKIN 3,371,053

MULTIGELLULAR PLASTIC PARTICLES AND DISPERSION-S THEREOF Filed Aug. 9,1965 2 Sheets-Sheet 2 INVENTOR BETTY LOU RA SKIN BY 0 :60? a? 00ATTORNEYS United States Patent ABSTRACT OF THE DISQLOSURE Multicellular,solid, substantially spherical polymeric organoplastic particles havinga particle size of from one to one thousand microns and aerosols of suchparticles, are produced by injecting a composition capable of forming asolid polymeric organoplastic foam into a high velocity gas stream. Themulticellular particles can be recovered from the aerosol so produced.

This application is a continuation-in-part of my application Ser. No.207,729, filed July 5, 1962, now abandoned, which is acontinuation-in-part of my applications Ser. No. 7,568 filed Feb. 9,1960, and Ser. No. 798,959, filed Mar. 12, 1959, both of which are nowabandoned.

This invention relates to multicellular plastic particles, todispersions of such particles in air and other gases and to methods ofmaking the particles and dispersions.

I have found that when a composition capable of form. ing a polymericorganoplastic foam is introduced into a rapidly moving stream of gaswhich has a temperature above the foam-developing temeprature of thecomposition, a dispersion of multicellular polymeric organoplasticparticles is formed which may be utilized as such and from whichmulticellular plastic particles of the invention may be separated bysuitable means. This composition comprises a polymeric material orsuitable starting materials or reactants which are capable of formingsuch polymeric material, and which polymers or starting materials respectively, are, due to their composition or due to the presence of asuitable adjuvant, capable of foaming or expending.

The method of the invention not only makes it possible to vary the sizeand density of the rnulticellular plastic particles independently overwide ranges but it also permits other characteristics of the particlessuch as color, surface reflectance, hygroscopicity and the like to bevaried independently of the size and density of the particles.

The expanding or blowing component of the foamforming compositions maybe added to the plastic foamforming compositions as such; it may begenerated by a reaction, such as a condensation reaction, betweencomponents of the plastic foam-forming composition; or it may begenerated by the reaction of components added to the composition forthis purpose alone, all of which is well known in the art of producingplastic foams and will be more particularly described hereinafter. Theword blowing agent as used hereinafter is understood to include suchexpanding or blowing components.

In general, foam-forming compositions are known to produce virtually anytype of polymeric organoplastic in foam form. In accordance with thepresent invention, such foam-forming compositions may be utilized toproduce aerosols and particles. Some types of compositions may beutilized in a variety of ways, and this fact greatly adds to theadaptability of the invention to a wide variety of materials and uses.For example, blowing agents which expand by evaporation, such as water,acetone, methyl chloride and other chlorinated and/or fluorinated lowerhydrocarbons, or blowing agents which decompose on heating with theformation of gases, such as organic azo and nitroso compounds, areparticularly useful in imparting foaming properties to compositions suchas vinyl chlorides, phenolformaldehydes, urethanes and styrenes whichform thermoplastic and thermosetting polymers. The organic isocyanatesare also useful foaming agents in various types of plastic wherein theyreact, for example, with alcoholic or carboxylic acid components, withthe formation of carbon dioxide. Instead of, or in addition to, theagents mentioned above, air orother gas such as helium may be whippedinto a foam-forming composition, such as phenol-formaldehyde orpolyvinyl chloride, which is then injected into the gas stream where itis hardened by the action of the heat of the gas stream, which may beaided by the addition of a polymerization catalyst or hardening agent.

Blowing agents which react with other substances to produce gases mayalso be used, for example, ammonium salts which liberate ammonia whenreacted with bases such as potassium hydroxide. One or more solid,liquid, or gaseous blowing agents may be used alone or in combination orin association with other solids, liquids, or gases. The nature of thegas stream may be such that it, too, may in some chemical way contributeto the forma tion of the multicellular plastic particles. For example,it may enhance hte polymerization, expansion, foaming, or curing of theparticles. The foaming agents or a portion thereof may also be injectedinto the foam-forming compositions in the conduit by which thecompositions are conveyed into the gas stream.

Another example of the variety of ways in which the compositions may beutilized is to control the amount of certain components and/ or the typeof curing or hardening so that when the particles or aerosols areproduced they are still somewhat tacky, though solid, and may adhere toa particular surface before becoming fully cured or hardened. Forexample, this technique can be used to coat glass and paper withpartially-cured. multicellular particles of urethane foam without theuse of special adhesives. The amount of amine catalyst ordinarily usedin this type of composition to produce fully cured mnlticellularparticles of urethane foam may be reduced so as to produce the desiredeffect.

These and other illustrative compositions capable of forming polymericorganoplastic foams useful in the practice of the invention aredescribed in the following US. patents:

Thermoplastic polymers:

2,737,503Sprague et al. 2,744,076-Breuer et al. 2.,776,265-Fu1ler.2,797,443-Carlson. 2,804,435-Reed.

2, 816,827Roth.

Urea-formaldehyde:

2,789,095-Lindvig.

Phenolics:

2,446,429-Nelson et al. 2,608,536Sterling.

2,65 3,139Ster1ing. 2,744,875Th0mas et al. 2,772,2464imon et al.2,798,054-Aimon et al. 2,802,240-Thomas.

Isocyanate-containing compositions:

2,5 77,279 Simon et al. 2,577,280-Simon et al. 2,5 77,3 81Stirnernann.2,602,783-Simon et al. 2,642,403Sin1on et al. 2,698,83 8Simon et al.2,706,311-Durst et al.

r 3 Isocyanate-containing compositions:

2,7 40,743-Pace. 2,787,601Detrick et al. 2,78 8,3 3 5B arthel.2,802,795Simon et al. 2,842,506-Roussel. 2,846,408-Brochhagen et al.

Epoxy resins:

2,7 39,134Parry et al. 2,831,820-Aase et a1. Silicones:

2,813,839-Rust et :11. 2,83 3,7 32Weyer.

Filler and pigment components incorporated in some of the compositionsof the patents cited above will usually be omitted from the compositionsfor the purpose of the present invention, but these and other filler andpigments, as well as other ingredients, such as fire retardingmaterials, may be added to the compositions to vary the properties ofthe dispersions or of the dispersed particles for particular purposes.For example, the addition of finely divided flake metallic pigments,such as aluminum flake, may be added to vary the reflectance of thesmoke or the separated particles to light or other radiation.

The stream of gas into which the compositions capable of formingmulticellular polymeric organoplastic particles are injected may beprovided in a variety of ways. Gas turbines of the portable type providea very advantageous source of gases for use in making cellular plasticparticles by the method of the invention at any desired location.However, exhaust gases from internal combustion engines, jet, turbojet,and rocket motors may be used. The source of the gas stream is notimportant except as a matter of convenience and economy. The temperatureof the gas stream must, of course, be sufiicient to effect or sustainthe foam-forming reaction.

Typically, the foam-forming composition is injected into the gas streamin liquid form, either in a single stream or in two or more streams eachcontaining the same or different components of the foam-formingcomposition. According to the character of the composition, normallysolid compositions or components may be liquefied by warming, by addingsolvents thereto, or a liquid" or finely divided solid composition maybe dispersed in a carrier liquid or gas and injected or blown into thehot gas stream.

The theory by which multicellular plastic particles are made accordingto the present invention has not been ascertained. However, it has beendetermined that by injecting the foam-forming compositions into a streamof gas which moves at least at approximately sonic velocity,multicellular particles are produced. Thus, while it is quite possiblethat a more basic physical principle is responsible for formation ofmulticellular particles, that result has been found to occur when,according to the invention, sonic or substantially sonic velocities areempolyed.

The multicellular plastic particles may be separated from the carriergas by any of a variety of means such as centrifugal or cycloneseparators, bag filters, electrical precipitators and the like. Thechoice of separating devices will depend to some extent on the characterof the particles and of the carrier gases but in general the type ofseparator will not be critical.

Illustrative examples of the method of the invention will be moreparticularly described with reference to the accompanying drawingswherein:

FIG. 1 is a diagrammatic representation of apparatus suitable for use inpracticing the method of the invention.

FIG. 2 is a perspective view of muticellular particles of the inventionshowing closed-cell type particles based on photographs thereof.

In FIG. 1, is a compressor and 11 is a turbine on the same shafttherewith, with a combustion chamber 12 heating compressed air from thecompressor on the way to the turbine in accordance with the commonarrangement. Hot exhaust gases from the turbine pass through venturi 13.Tanks 14 and 15 contain liquid-foam-forming compositions or componentsthereof. Tanks 14 and 15 are supplied with compressed air through line21 which serves to force the contents of the tanks through lines 16 and17 into venturi passage 13 wherein the compositions are brought tofoaming temperature and are converted into dispersions of finemulticellular particles of foamed plastic.

The gaseous dispersions thus formed may be conducted tangentially intocyclone separator 18, wherein the par ticles are separated bycentrifugal action, the particles being deposited in hopper 19 and thecarrier gases passing out through outlet tube 20. The collectedparticles are spherical, or at least substantially so. Furthermore, asshown in FIGURE 2, each particle is multicellular with a plurality ofhollow cells therein. In some cases, as shown in FIGURE 2, the severalhollow cells are mostly closed whereas, in other cases, the severalcells may be partially or fully open. In either event, however, theparticles are multicellular and have an interior composed of aninterconnected network of the plastic material formed by the juncture ofadjacent cells.

The following specific examples are illustrative of the principles ofthe invention:

Example I One hundred pounds of a thermosetting, partiallyreacted phenolaldehyde resin (made by heating one mol of phenol with two and one-halfmols of formaldehyde, as 40% aqueous solution, in the presence of 0.05mol of sodium hydroxide for two hours at about 85 C., neutralizing withlactic acid and dehydrating under vacuum to about 10% of Water) is mixedwith seven pounds of isopropyl ether, and one pound of Tween 40 Wettingagent (polyoxyalkylene ether of sorbitan monopalmitate) in tank 14 ofthe apparatus of the drawing and a catalyst composition of 50 parts of66 B. sulfuric acid and 7 parts of phosphoric acid in 50 parts of waterare placed in tank 15.

The compressor-turbine system is started up and adjusted to give astream of exhaust gases at about 900 F. at a velocity of about 1,075 ft.per second. When the resin mixture and the catalyst composition are fedinto the venturi section at the rate of about 22 parts of the catalystcomposition to parts of the resin mixture, a dispersion is formed fromwhich pinkish spherical multicellular particles of phenolic plastic arecollected in the cyclone separator. The collected particles are partlyopen celled and partly closed celled. They range from about 5 to about1,000 microns in diameter with an average diameter of about 70 microns.The bulk density of the particles is about 0.01 gram per cc.

FIG. 2 is a greatly enlarged reproduction of an illustrative group ofmulticellular phenol formaldehyde plastic particles produced by theprocedure of Example I, but shown as being of fully closed cellconfiguration.

Example II When furfuryl alcohol is added to the resin composition ofExample I in the proportion of 10 parts of furfuryl alcohol and 6 partsof isopropyl alcohol to 84 parts of the phenol-formaldehyde resin andthe composition is injected into the hot exhaust gas stream as inExample I, black multicellular plastic particles are collected in theseparator.

Example III When a two-component urethane foam composition consisting,as to component A in tank 14, of 78.8 parts of an isocyanate terminatedpolyether prepolymer and 21.2 parts of trichlorofiuoromethane, and, asto component B in tank 15, of 66.4 parts of a polyether resin containinga polypropyleneoxide chain, 20.7 parts of trichlorofluoromethane and 3.3parts of triethylamine as catalyst, is fed to the venturi section of theapparatus of the drawing as described in Example I, white multicellularplastic particles are produced. The collected particles are of closedcell structure and consist of clusters up to about 700 microns indiameter of closed cell particles about 12 to 20 microns in diameter.Increasing the proportion of catalyst increases the degree of expansionof the particles.

The trichlorofluoromethane reduces the viscosity of the liquidcomponents and also acts as a blowing agent.

Example IV Carbon dioxide at 300 to 400 pounds pressure is whipped intoa mixture of 100 parts of polyvinylchloride and 100 parts of tricresylphosphate and the mixture is sprayed into a hot gas stream as describedin Example I. Multicellular particles of polyvinylchloride are collectedin the separator.

The density of the multicellular particles can be varied by varying thenature and proportion of the resin or resin-forming composition and theblowing agent, the reaction temperature and other variables. It ispossible to produce multicellular plastic particles having a density aslow as or lower than that of air (0.0012 gm./cc.). This makes possiblethe production of dispersions of low fallout rates with particles ofrelatively large size.

While the relative volume of the hot carrier gas stream does not appearto be critical, the temperature must be high enough to eifect a rapidformation of foam, and both relative volume and temperature may aifectthe size and density of the particles. By variation of the temperatureand volume relationships, design of the injection nozzles, and thecharacter and amount of the blowing agents, it is possible to vary thesize and density of the particles over a wide range. For example, theinjection nozzles may be placed at various locations and attitudes withrespect to the gas stream. Further, where more than one stream isemployed, the streams may be placed to cause mutual impingement thereofas, for example, by placing two injection nozzles in opposition.

Where the foam-forming composition is utilized as two or more streams,and where such streams are placed such as to cause mutual impingement,mixing action is believed to be enhanced to such an extent thatmulticellular particles according to the invention may be obtainedwithout necessarily utilizing a sonic velocity gas stream. Such resultwould be due to the additive mixing action of impingement and ofturbulence due to the gas stream flow. The relative velocity, one to theother, of the two or more streams would affect the degree of mixing orturbulence due to impingement and, depending on the magnitude of thisrelative velocity, the velocity of the gas stream could be lowered andyet the total cumulative result of gas velocity and impingement couldcause sufficient turbulent mixing to produce multicellular particlesaccording to the invention.

The average particle size may be varied from about 1 micron to over1,000 microns and the cells may be open or closed, according tooperating conditions selected according to the use to which theparticles are to be put. Gas velocities in the reaction zone at or nearsonic velocity result in the formation of multicellular particles andare particularly desirable in maintaining smooth operation. Instead ofusing spray nozzles to disseminate the resin compositions in the gasstream, dissemination may be effected in other ways, as by the use ofrapidly rotating members.

Among the uses of the plastic particle dispersions of the invention arethose dependent on the reflective or absorbent power of the dispersionsfor radiant energy. For example, they may be used to prevent frostdamage to crops by preventing the radiation of heat from orchards andthe like. They may, of course, be used for the usual purposes ofpresently available smokes, such as smoke screens, smoke signals, skywriting and the like with the dried advantage of the low settling ratesdue to the low density to size ratios of the dispersed particles in thedispersions of the invention. Other uses will depend on the utilizationof the dispersed plastic particles as eflicient carriers for reactivesubstances, such as silver iodide for cloud seeding or insecticides forsanitation or crop protection. For the production of relatively stabledispersions of the particles in gaseous media particle sizes in therange of from about 1 micron to about microns are particularly suitable.

The multicellular plastic particles of the invention have a wide varietyof uses.

They may be reconstituted into smoke-like dispersions by redispersion ingaseous carriers, either in the form in which they are collected orafter coating or other treatment to vary their color, reflectance or thelike for use in signalling, smoke screening, sky writing, sky projectionand the like, or to incorporate pesticides for sanitation or cropprotection or reactive substances, such as silver iodide for cloudseeding.

The collected particles may be used as light weight fillers, expandersor texturing agents in inks, paints, enamels and other coatingcompositions, and in rubber and plastic compositions.

They may be used as fillers in paper stock or in paper coatingcompositions.

They may be used as soil conditioners, either as collected or afterincorporating pesticles, plant nutrients or coloring substances.

They may be used as light Weight fillers for tires and as pourable,lightweight insulation.

The particles may be collected on a layer or coating of an adhesive orbinder composition to provide useful coatings of variable texture,transparency and gloss, and useful coatings may be produced by impingingthe gas stream bearing the particles on a collecting surface before theparticles are fully hardened.

Depending upon the point in time that the particles are collected, theincompletely cured particles may or may not be fully expanded, and thecollection may be accomplished at a time such that the particlescollected may be subsequently fully expanded.

I claim:

1. A method of making dispersions of finely divided multicell-ular solidpolymericorganoplastic particles having a plurality of hollow cellstherein comprising the steps of injecting a foam-forming composition,said composition being capable of forming a solid polymericorganoplastic foam, into a stream of rapidly moving gas, said gas movingat least at approximately sonic velocity and being at least at atemperature necessary to cause foam-development of the composition, todisperse said composition in said rapidly moving ga stream, andmaintaining said dispersed composition in contact with said gas whilesaid composition forms a dispersion of multicellular solid polymericorganoplast-ic particles having a plurality of hollow cells therein.

2. A method as defined in claim 1 in which diiferent components of thefoam-forming composition are separately injected into the stream of gas.

3. A method as defined in claim 2 in which one of the separatelyinjected portions of the foam-forming composition rincludes a catalystfor the hardening of the polymeric organoplastic.

4. A method of making multicellular solid polymeric organoplasticparticles having a plurality of hollow cells therein comprising thesteps of injecting a foam-forming composition, said composition beingcapable of forming a solid polymeric organop lastic foam, into a streamof rapidly moving gas, said gas moving at least at approximately sonicvelocity and being at least at a temperature necessary to causefoam-development of the composition, to disperse said composition insaid rapidly moving gas stream, maintaining said dispersed compositionin contact with said gas while said composition forms a dispersion ofmulticellular solid polymeric organoplastic particles having a pluralityof hollow cells therein, and thereafter collecting the particles.

5. An aerosol comprising a dispersion in a gaseous medium of solid,mu'lticellular, and at least substantially spherical polymericorganoplastic particles having a plurality of hollow cells therein andhaving an average particle size of from one micron to about one thousandmicrons.

6. An aerosol according to claim 5 wherein the polymeric organoplasticis a thermoplastic synthetic resin.

'7. An aerosol according to claim 5 wherein the polymeric or-ganoplasticis a thermosetting synthetic resin.

8. An aerosol according to claim 5 wherein the polymeric organoplasticis a rubber.

9. A multicellular, solid, and at least substantially sphericalpolymeric organoplastic particle having an average particle size in therange of from about one micron to about one thousand microns and havinga plurality of hollow cells therein and an at least partially closedcell structure.

19. A multicellular, solid, and at least substantially sphericalpolymeric organoplastic particle having an average particle size in therange of from about one micron to about one thousand microns and havinga plurality of hollow cells therein and an at least partially open cellstructure.

11. A multicellular, solid, and at least substantially sphericalpolymeric organoplastic particle having a plurality of hollow cellstherein and having a particle size of from one to about one thousandmicrons.

12. A multicellular particle according to claim 11 wherein theorganoplastic particle comprises a thermoplastic resin.

13. A multicesllular particle according to claim 11 having a density offrom about 0.0012 to about 0.01 gram per cc.

14. A multicellular particle according to claim 11 wherein theorganoplastic particle comprises a thermosetting resin.

15. A multicellular particle according to claim 14 wherein thethermosetting resin is selected from the group consisting ofurea-formaldehydes, phenol-formaldehydes, urethanes, epoxies andsilicones.

References Cited UNITED STATES PATENTS 3,037,903 6/1962 Baumann et al.2602.5 3,038,867 6/1962 Czepiel 2602.5 3,210,239 10/1965 Ebert et al.260-25 MURRAY TILLMAN, Primary Examiner.

GEORGE F. LESMES, Examiner.

M. FOELAK, Assistant Examiner.

